A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
Abradable coatings are utilized in compressor and turbine sections on inner surfaces of a casing proximate a rotating airfoil. The abradable coating is utilized where minimizing clearances between a static casing structure and the tip of a compressor or turbine blade is desirable to increase engine efficiency. The abradable coatings are worn away by abrasive tips in the compressor and turbine sections to provide the desired clearance. The abradable coating not only provides closer clearances but also adjusts those clearances during engine operation to accommodate changes due to loading and thermal changes. While some level of wear can be estimated based on engine operation, such estimates of incursion depths of an airfoil tip into the abradable coating may not be as accurate as desired. The depth of incursion into an abradable coating as well as dynamic changes in abradable coating wear provides information that can be utilized to determine abradable coating depths and to monitor engine operating efficiencies and changes.
Turbine engine manufacturers continue to seek further improvements to engine performance including improvements to thermal, transfer and propulsive efficiencies.